Wellhead casing hanger assembly

Abstract

Opposed pairs of sockets are formed by the bottom surface of the slip housing and the top surface of the bottom ring of a casing hanger assembly. Vertical holes are provided in the elastomer seal element which is sandwiched between the slip housing and bottom ring. Each pair of sockets and corresponding seal element hole form a socket chamber. Rigid, motion-limiting pins are positioned in the socket chambers. Each pin has side and bottom clearances with the chamber side and bottom walls. The pins are therefore initially free floating, to allow the seal element to move to accommodate oversized casing; but the pins take up the casing load as the slip housing descends and limit its downward travel, thereby preventing excessive compression of the seal element, which can lead to casing damage.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. In a casing hanger assembly mounted for use in a wellhead to suspend casing from an internal landing shoulder of a casing bowl, said assembly comprising a bottom ring for seating on the landing shoulder, an annular elastomeric seal element seated on the bottom ring, an annular slip housing seated on the seal element and slips, supported by the slip housing, for engaging and suspending the casing, said slip housing being operative to partly compress the seal element so that it expands radially and seals against the casing and casing bowl, the improvement comprising: said bottom ring having an annular top surface having a plurality of downwardly extending sockets spaced along its length;   said slip housing having an annular bottom surface having a plurality of upwardly extending sockets positioned in opposed relation to the bottom ring sockets so that pairs of opposed sockets are provided;   said seal element having a plurality of vertical holes corresponding with the socket pairs so that each hole and its associated pair of opposed sockets combine to form a socket chamber having side, bottom and top surfaces;   a plurality of rigid pins, each disposed in free floating condition in a socket chamber and extending through the full extent of the seal element hole forming part of that chamber, each such pin having side clearance with the chamber side surface and end clearance at one end of the chamber;   whereby the un-compressed seal element and pins may shift laterally to accommodate casing having oversize diameter, said pins being operative to contact the bottom ring and transfer casing load from the slip housing to the bottom ring when the seal element is partly compressed, thereby limiting seal element compression.   
     
     
       2. A casing hanger assembly for use in a wellhead to suspend casing from an internal landing shoulder of a casing bowl, comprising: a bottom ring for seating on the landing shoulder, said ring having an annular top surface having a plurality of downwardly extending sockets spaced along its length;   an annular slip housing for positioning above the bottom ring in spaced relation thereto, said slip housing having a bottom surface having a plurality of upwardly extending sockets positioned to be in opposed relation to the bottom ring sockets so that pairs of opposed sockets are provided;   an annular elastomeric seal element positionable between the bottom ring and slip housing, said seal element having a plurality of vertical holes corresponding with the socket pairs so that each hole and its associated pair of opposed sockets combine to form a socket chamber having side, bottom and top surfaces;   a plurality of rigid pins, each positionable in one of the socket chambers, each pin having an upset head and a shank, the head being supported by the seal element, said head having a side clearance with the socket chamber side wall and being in contact with its top wall, the shank having side and bottom clearances with the socket chamber side and bottom surfaces when the casing hanger is assembled; and   slips, supportable by the slip housing, for engaging and suspending the casing and transferring casing load to the slip housing;   whereby the un-compressed seal element and pins may shift laterally to accommodate casing having oversize diameter, said pins being operative to contact the bottom ring and transfer casing load from the slip housing to the bottom ring when the seal element is only partly compressed by downward travel of the loaded slip housing.   
     
     
       3. The casing hanger assembly as set forth in claim 2 wherein: some of the pins have vertical bores extending therethrough;   the bottom ring has vertical bores extending therethrough corresponding with the pin bores;   the slip housing has vertical threaded bores, extending thereinto from its bottom surface, corresponding with the pin bores; and   a plurality of cap screws are provided for connecting together the bottom ring, bored pins and slip housing by extending from the bottom ring, through the pins and into the slip housing.   
     
     
       4. The casing hanger assembly as set forth in claims 2 or 3 wherein the seal element has a rectangular cross-section and right angle corner rings formed of stiff material are mounted to the corners of the seal element to reinforce it.